This paper discusses the sulfate resistance and frost of mass hydraulic concrete which containing fly ash, superplasticizer and a novel MgO-bearing expansive agent (HNM), at same time, the mechanisms and processes of sulfate attack on it have been proposed. Results showed that using a water/binder ratio of 0.48 in RCC containing 50 % fly ash and 8 % HNM a durability factor of over D300 can be achieved and sulfate resistance may be improved slightly.